The present invention relates to an alarm transmission system, comprising at least a detection unit, equipped with detectors capable, when energized, of delivering electrical signals, a signal transmission unit for transmitting the signals sent by the detection unit or units, and at least one receiver remote from the detection unit, for receiving the signals transmitted by the transmission unit.
Numerous systems are known which are intended for detecting any change occurring in the environment where a detector is located and for triggering an alarm in a spot remote from where the detector is located. Such systems generally require a transfer of information by telephone. The signals sent by the detectors when these are energized, are transmitted in coded form by telephone wires connected to a central monitoring station. Such systems, which are relatively complex, do not permit an instant intervention on the spot where an anomaly is detected, due to the necessity of an entirely centralized transmission by telephone. Moreover, the detectors need to be installed in a fixed station.
It is also known to equip detectors with radio-link transmission means for remotely transmitting an alarm signal. Such detectors, which are also fixedly installed, generally have a poor transmission range and can only transmit a signal to a receiver situated in the immediate vicinity of the detector, without permitting the centralizing or identifying of the information sent when several detectors installed apart from one another are used.
It is also known from French Patent No. 2 234 622 and from its first Patent of Addition No. 74 27 456 to use a telemonitoring system wherein a central unit, mounted in a vehicle, can be successively in contact with permanent peripheral units equipped with emitting receiving means. Such a system however is limited in versatility due to the fact that there is only one central unit which can be connected to the different peripheral units and that the latter can only send information if they are actively urged, this actually implying that they are themselves equipped with radio reception means.
It is precisely the object of the present invention to overcome these disadvantages and to propose an alarm monitoring and transmission system which is particularly easy to install and permits both to centralize the information supplied by the different detectors used and to ensure the reception of the information sent by the detectors from mobile receiving points situated at varying distances from the monitored zones.
A further object of the invention is to produce an alarm monitoring and transmission system which is entirely autonomous and independent of the environment to be watched, permitting an overall monitoring whilst increasing the reliability of operation and the rapidity of intervention when an alarm is released.